Removal of nuclides and boric acid from simulated radioactive wastewater by forward osmosis

Abstract

In this paper, the removal of nuclides and boric acid from the simulated borate-containing radioactive wastewater was studied using forward osmosis (FO) process. The effect of membrane materials and their orientation, as well as borate concentration on the flux and retentions of nuclides and boric acid was determined. The results indicated that cellulose triacetate with embedded polyester screen support (CTA-ES) membrane had highest Co2+ retention (99.62–99.69%) and Sr2+ retention (96.90–97.85%) when boric acid concentration increased from 0 to 2400 mg L−1 and the active layer facing feed solution (AL-FS) mode was used. Cellulose triacetate with a cast nonwoven support (CTA-NW) and CTA-ES membranes had equivalently high Cs+ retention (∼95%). Thin-film composite with embedded polyester screen support (TFC-ES) membrane had lowest Cs+ retention (below 40%). For both CTA membranes at AL-FS mode, the nuclide retentions did not change obviously with borate concentration. However, the nuclide retention for TFC-ES membrane was affected by borate concentration. Borate retention was lower than 37% for three membranes. For both CTA membranes, borate concentration had no obvious influence on the trans-membrane osmotic pressure, water flux and reverse NaCl flux. CTA-ES membrane has potential for the treatment of borate-containing radioactive wastewater due to its highest nuclide retention, boric acid flux and water flux.